The broad objective of the proposed research is to understand the mechanism mechanisms responsible for the carcinogenicity of two nitrated polycyclic aromatic hydrocarbons (NO2-PAH), 1-nitropyrene (1NP) and 3-nitro-fluoranthene (3NF). These compounds have been shown to be carcinogenic in adult animals; however, as is pointed out in more detail in the Significance section, 1NP is more carcinogenic and leukemogenic in young animals. 1NP is susceptible to activation through both C-aryl oxidation and especially nitroreduction. Additionally, it has been observed that upon administration to pregnant animals, 1NP can cross the placenta and is metabolized in the fetal tissue. The long term objective is to understand the specific metabolic pathways by which these environmental contaminants are metabolized in young and adult rabbits and rats, determine the capabilities of these pathways to activate/deactivate the compounds in human tissue, and provide an understanding of the potential risk of these compounds to humans. The specific aims of the proposal are designed to systematically dissect the activation and deactivation pathways in fetal, neonatal, and adult rabbits and rats, and human tissue. The specific aims are: (1) determine the enzymes involved in the metabolism of 1NP and 3NP in rabbit liver, lung, spleen and marrow tissues; (2) determine the age and sex differences in these pathways; (3) extend these studies to the rat where a more critical evaluation of the carcinogenicity exists; (4) determine the presence of these pathways in human tissue samples obtained post- partum (placenta), post-mortem, and from pathological samples; (5) from the above information, reevaluate DNA adduct formation in the rat, and quantitate the formation of adducts using (3H)1NP and (3H)3NF. Specific methodologies include the incubation of (3H)1NP and (3H)3NF with whole cell homogenates, and the microsomal and cytosolic fractions of the specific tissues in question, evaluating (a) oxidative metabolism, (b) nitroreductive metabolism, and (c) potential or RNA or DNA binding. Certain pathways will be inhibited with specific metabolic inhibitors to determine their contribution to the metabolism of 1NP and 3NF.